The difficulty with this type of leadthrough lies in, among other things, the fact that glass and metal generally have different coefficients of thermal expansion, which can lead to temperature stress and, consequently, to fissures in the glass material. The use of certain alloys, such as iron-nickel alloys in particular, which have a coefficient of temperature expansion matched to the glass, is a known measure for counteracting this problem. However, the problem then emerges that such alloys are not optimal with regard to the conductivity thereof. In order to improve conductivity, particularly in order to carry high current, an electrical leadthrough was manufactured in the past having a metal tube of such an alloy. Then a rod of a material having high conductivity, particularly copper, or brass or bronze was soldered into the tube in a second step.
However, a disadvantage of such a leadthrough is that a reheating when soldering still leads to thermal stress, which then considerably degrades the temperature resistance and long-term stability of such a leadthrough.